Silicon carbide is expected to be used as a material for next-generation semiconductor devices. Silicon carbide has better physical properties than silicon in that its band gap is 3 times larger than silicon, breakdown electric field intensity is about 10 times better, and thermal conductivity is about 3 times better. When these characteristics are utilized, for example, metal oxide semiconductor field effect transistors (MOSFETs) capable of operating at higher breakdown voltage, at lower loss, and at higher temperatures can be realized.
Vertical MOSFETs have body diodes. For example, when MOSFETs are used as switching elements connected to inductive loads, even when the MOSFETs are nominally turned off, reflux currents can flow through the body diodes.
However, when reflux currents are flowed through the body diodes, stacking faults can grow in silicon carbide layers used to form these MOSFETS due to recombination energy of carriers, and thus there is a problem that on-state resistance of the MOSFETs will increase. The increase in the on-state resistance of MOSFETs results in a reduction in reliability of MOSFETs.